Start an asynchronous write. The data being written must be valid for the lifetime of the asynchronous operation.

template<
    typename ConstBufferSequence,
    typename WriteHandler = default_completion_token_t<executor_type>>
DEDUCED async_write_some(
    const ConstBufferSequence & buffers,
    WriteHandler && handler = default_completion_token_t< executor_type >());

Completion Signature

void(asio::error_code, std::size_t)